The HAR-1 gene differs by two base
pairs between chickens and chimps, one base pair between chimps and
rabbits and one base pair between rabbits and mice. Human
HAR-1 differs from chimps by 18 base pairs. There is no variation of
these base pairs among all humans.

HAR-1 is expressed during early fetal neocortex (intelligence,
mathematics, language, imagination) development, and correlates with
the production of the Reelin protein, which is
responsible for the development of neuron interconnections.
The odds against a natural selection or mutation cause for the sudden
appearance of the human HAR-1 are 1/782,917,642,535,650,449.
It's not likely viral, so some speculate that it is alien.